Size of Allen socket for brake job

I cannot tell anything from our databases. If it is an allen bolt, my best guess would be 8mm (fairly popular size). You could measure across the diagonal of the bolt and get a good ball park idea. Buy the two or three closest ones that you find and return the ones that you do not use. You can buy just about every automotive tool that you will need for at AutoZone, Advance Auto, O'Reilly Auto Parts, NAPA, or Sears. If you are getting into auto mechanics and are going to be learning things, then you would be smart to buy a mechanic's tool set. I buy Sears Craftsman myself because they are pretty tough and have a lifetime warranty on them. When I worked there, we routinely replaced wrenches and pliers that were obviously forty years old.